In general, the washing machine washes by using composite action of friction between water circulation and laundry caused by forced circulation of washing water, softening action of detergent, and impact applied to the laundry by a pulsator.
Referring to FIG. 1, such a related art washing machine is provided with a body 10 forming an exterior of the washing machine, an outer tub 20, a washing tub 30 also used as a spinning tub, a pulsator 40, and power transmission means for transmission of power from a motor to the washing tub 30 or the pulsator 40.
The outer tub 20 is suspended in the body, for holding washing water.
The washing tub 30 is rotatably mounted in the outer tub 20 with an appropriate space thereto, and has a plurality of pass through holes 31 for communication with an inside space of the outer tub 20.
The pulsator 40 is rotatably mounted on a center of an inside bottom of the washing tub 30.
The power transmission means is provided with a clutch 50 and a belt 70.
The clutch 50 is fixedly secured to an underside of the outer tub 20, and coupled to the pulsator 40 and the washing tub 30 with a shaft, for rotating the pulsator 40 or the washing tub 30, selectively.
The motor 60 is mounted on one side of an underside of the outer tub 20, for transmission of power to the clutch 50.
In the meantime, on one side of an upper side of the body 10, there is a water supply hose 12 connected thereto, and on one side of the underside of the outer tub 20, there is a drain hose 14 connected thereto for draining washing water.
On top of the body 10 of the washing machine, there is a display window (not shown) for displaying a washing course selected by the user, a washing progressing state, a time period, and the like.
In the washing machine, once a washing mode is selected in a state laundry and detergent is introduced in the washing tub 30, in general, washing, rinsing, and spinning are made automatically according to a control signal from a controller (not shown).
That is, once a washing mode is selected, a water supply valve 11 on the water supply hose is opened, to supply washing water to the washing tub 30 through the water supply hose 11. In this instance, the washing water may be supplied through a powder detergent box, to supply the powder detergent to the washing tub 30, together with the washing water.
In this instance, since the washing tub is in communication with the outer tub 20 through the plurality of pass through holes 31 in the outside circumferential surface, as described before, the washing water supplied to the washing tub 30 is introduced to the outer tub 20 through the pass through holes 31 in the washing tub 30, too.
If the washing water is filled in the outer tub 20 and the washing tub 30 to a certain level by the foregoing process, the water supply valve 11 is closed, to stop the water supply, and the motor 60 fixedly secured to one side of the underside of the outer tub 20 is driven, to drive the clutch, to rotate the washing tub 30 or the pulsator 40 selectively depending on washing cycle.
Accordingly, the laundry in the washing tub 30 is washed by rotation force of the pulsator 40, friction force with an inside circumference of the washing tub 30, and a separative power of the detergent.
Then, when the washing cycle is finished by above actions, the drain valve 13 on the drain hose 14 is opened in response to a control signal from the controller (not shown), the washing water used for the washing is drained from the outer tub 20 and the washing tub 30 to an outside of the body 10 through the drain hose 14.
Thereafter, a rinsing cycle is performed, in which rinsing is repeated a few times in a state washing water is supplied to the washing tub 30. In this instance, since the washing water may be supplied through a bleaching agent box, the bleaching agent may be supplied to the washing tub 30, together with the washing water.
In this instance, the washing machine may also be controlled such that, following draining, short time period of spinning and re-supply of new washing water may be made between rinsing cycles, for improving rinsing efficiency.
Moreover, after such a rinsing cycle is finished fully, a final spinning is performed, when the washing tub 30 and the pulsator 40 are rotated at a high speed in a state the washing water used in the rinsing is naturally drained to an outside of the washing machine.
According to this, water is extracted from the laundry to the outer tub 20 through the pass through holes 31 in the washing tub 30 by centrifugal force caused by the high speed rotation of the washing tub 30 and the pulsator 40.
Moreover, in this instance, since the drain valve 13 under the outer tub 20 is opened, the water from the laundry is drained to an outside of the washing machine through the drain hose 14.
Above spinning cycle is performed for a preset time period, and once the spinning cycle is finished, operation of the washing machine is stopped fully, to finish the washing course.
In the meantime, other than above type and structure of washing machine, there are a so called a tub rotating type of washing machine in which the washing tub 30 rotates in a direction opposite to a rotation direction of the pulsator, and a centrifugal penetration type of washing machine in which the washing is made by water penetrating through the laundry by centrifugal force generated by high speed rotation of the washing machine directly connected to a motor.
Moreover, though not shown, the related art washing machine may be provided with a device for supplying steam to the washing tub during washing or before the washing for soaking the laundry. By supplying hot steam to the laundry, the washing effect is enhanced.
However, regardless of the washing types and structures of above washing machines, there has been a problem in the related art in that dirt from the laundry during washing, and remains and mixtures of detergent and softener remain on inside/outside walls of the washing tub 30, and on an inside wall of the outer tub, to cause re-contamination of the laundry, to drop reliability of the washing machine in view of sanitary.
Moreover, bad odor is produced from microbes, such as fungus on the dirt when the tub is contaminated, to drop reliability of the washing machine in view of sanitary, too.
In general, as the washing machine is used for a long time period, dirt accumulates on the inside/outside surfaces of the washing tub 30 and the inside surface of the outer tub, to increase an amount as time goes by.
In the meantime, though there are washing machines having tub washing functions for resolving problems started from the tub contamination, the present washing machines having the tub washing functions have a poor tub washing efficiency as the tub washing course is progressed, ineffectively.
Particularly, if the washing tub washing is performed in a state the powder detergent is in the washing tub, the powder detergent produces foam, to impede rotation of the washing tub, putting a load on the motor that rotates the washing tub, to cause a power loss.
Moreover, the foam is liable to fail to be discharged with the washing water in draining of water, but stay in the washing tub, to contaminate the washing tub. That is, even if washing of the washing tub is finished, the foam is liable to stay in the washing tub, to contaminate the washing tub.